1. Field of the Invention
The invention relates in general to a page buffer and method of programming and reading a memory, and more particularly to a page buffer, in which a data change unit is used to change the value of the latch for the data of a lower page to have a high level, and method of programming and reading a memory.
2. Description of the Related Art
Multi-Level Cell (MLC) technology enables storage of multiple bits per memory cell by charging the poly-silicon floating gate of a transistor to different levels. This technology takes advantage of the analog nature of a traditional flash cell by assigning a bit pattern to a specific voltage range. MLC effectively reduces cell area as well as the die size for a given density. This ultimately leads to a significantly reduced unit cost-per-megabyte—one of the greatest benefits of this technology.
NAND flash memory in MLC application, capable of storing two bits per memory cell, requires a smaller chip area per cell, thus allowing greater storage densities and lower costs per bit than other flash memory. Therefore, how to design a page buffer circuit for the operation of NAND flash memory in MLC application is very essential for the flash-memory industries.